Why does everyone judge and reject this boy?

So there's a boy I know at school. He's new this year, a sophmore (I'm a senior). Everyone, and I mean literally EVERY ONE talks about how they thought he was cool at first, but how he started to get too 'weird' or 'creepy'. So now everyone avoids him and refuses to be his friend. My good friend Ranya is the worst of all, she constantly makes nasty comments about him and says that God told her to stay away from him. When everyone else talks to him, they see a freak. When I talk to him, I see a boy who perhaps has some quirks, but who is smart and kind. How is it that they can judge him so harshly?